Investigating activation of carbon fiber nonwovens for use as supercapacitor electrodes

Double-layer supercapacitors rely on the high specific surface area (SSA) of activated carbons. Typically, granular-activated carbon held together by polymer binder is used. As a potential alternative, this paper focuses on the potential use of commercially available carbon fiber nonwovens. A commercially available binder-free carbon fiber nonwoven was used initially, but surface area analysis revealed that no microporosity developed following the CO2 activation treatment. In order to investigate how the structure of the original carbon material impacted subsequent activation, polyacrylonoitrile (PAN) nonwovens were fabricated and carbonized in-house under controlled conditions (695, 895, and 1095 °C). Carbonization temperature was found to be a limiting factor, where higher carbonization temperatures led to lower potential for activation. Since commercially available materials are typically carbonized at unknown temperatures, and are likely carbonized at high temperatures to develop electrical conductivity, it is found that they are unlikely to form high SSA materials.